An insulated gate bipolar transistor (IGBT) is a device having the advantageous characteristics of an insulated gate structure of a metal oxide semiconductor (MOS) transistor and the high current density of a bipolar transistor.
In contrast to the MOS transistor, a conventional IGBT has a parasitic PNPN thyristor structure including a collector P, a drift region N, a base P and an emitter N.
However, if the sum of current gains of an NPN transistor and a PNP transistor provided in an equivalent circuit is equal to or greater than 1, a PNPN thyristor is turned on, so that turn-off performance by the gate may deteriorate, which is called latch-up.
Such a latch-up may restrict an SOA (safe operation area) of the IGBT and cause over current so that devices may be damaged.
Thus, there exists a need in the art for an improved IGBT.